1. Field of the Invention
This invention relates to terrain following apparatus for a vehicle, particularly, but not exclusively, suitable for providing an assisted terrain following capability to the pilot of an aircraft.
2. Discussion of Prior Art
A Terrain Referenced Navigation (TRN) system currently may be provided on vehicles such as aircraft to provide accurate position registration relative to the terrain by referencing a vehicle position within a digital terrain map database. By virtue of the digital map and by knowing the vehicle position accurately, it can also provide the vehicle driver or pilot with warnings of impending obstacles and cues for avoidance action. In the case of aircraft, these warnings can be of Impending Controlled Flight Into Terrain (CFIT) and cues for low level terrain following flight. Current Terrain Referenced Navigation systems for aircraft generally combine the aircraft Inertial Navigation System data with measurements of height above ground level, altitudes above mean sea level and terrain heights from the stored map data to provide high precision drift-free navigation. The high precision drift-free navigation generally includes accurate terrain referenced position registration, warning of impending controlled flight into terrain, situational awareness terrain display and terrain following cues.
However, such a Terrain Referenced Navigation system only provides advisory information to the vehicle driver such as an aircraft pilot and in aircraft flight conditions, which are unduly hazardous and in which the pilot may be operating at less than normal or peak efficiency, there is a need for ensuring that the vehicle driver or aircraft pilot is assisted in driving the vehicle or flying the aircraft with increased safety.
There is thus a need for a Terrain Following Apparatus for a vehicle which can effectively assist, in a safe manner, the vehicle operator to drive or fly the vehicle.
According to the present invention, there is provided a Terrain Following Apparatus for a vehicle including, means for effecting autonomous following of terrain by a vehicle, when the apparatus is operatively associated with the vehicle, a control device, operable by a person operating the vehicle, to engage and disengage the autonomous Terrain Following means, a Terrain Referenced Navigation system operable to provide navigation data for the vehicle, and validation means for validating the integrity of the navigation data, and for providing, when the integrity of the navigation data is validated, an output signal for permitting the control device, when engagedly operated by a person operating the vehicle, to operate the autonomous Terrain Following means to provide autonomous terrain following by the vehicle, and providing, when the integrity of the navigation data is invalidated, an output signal for preventing the control device when engagedly operated by a person operating the vehicle, from operating the autonomous Terrain Following means.
Preferably, the control device is an electromechanical device.
Conveniently, the control device is a non-latching device.
Advantageously, the control device is operable on failure of the device to disable autonomous operation of the vehicle.
Preferably, the navigation data provided by the Terrain Referenced Navigation system includes outputs of best estimates of position and height of the vehicle.
Conveniently, the validation means includes status means to establish whether the best estimates of position and height are within a desired operating range and to output a status result thereof, which status means is operable on a continuous basis to update the status result.
Advantageously, the apparatus includes communication means for communicating the status results to the person operating the vehicle, when the apparatus is operatively associated with the vehicle, to indicate desirability or otherwise of engaging the autonomous Terrain Following means.
Preferably, the validation means is operable automatically to deactivate the autonomous Terrain Following means on receipt of a negative status result, irrespective of whether the control device has been activated by the person operating the vehicle.
Conveniently, automatic deactivation of the autonomous Terrain Following means by the validation means occurs after transmission of the negative status result to the person operating the vehicle.
Advantageously, the communication means includes a video display and/or an auditory warning unit.
Preferably, the autonomous Terrain Following means is adapted for controllable connection to a movement control system of the vehicle.